Characteristics comparison between plasmid-harboring and chromosome-integrated recombinantSaccharomyces ceremsiae cultures

It is important to understand the differences in characteristics between plasmid-harboring recombinant yeast and chromosome-integrated recombinant yeast for the design and optimization of bioprocess employing recombinant yeast. In the present study, heterologous glucoamylase gene was inserted into yeast. The glucoamylase activity per gene copy number of chromosome-integrated recombinant yeast MMY2SUCSTA-I-5 was 3 to 6 folds higher than that of plasmid-harboring recombinant yeast MMY2SUCSTA. And the genetic stability of chromosome-integrated recombinant yeast (99%) was far better compared to plasmid-harboring recombinant yeast (65%). Better genetic stability and glucoamylase activity per gene copy number of chromosome-integrated recombinant yeast can provide advantages in higher final expression level, especially in continuous culture, compared to the plasmid-harboring recombinant yeast. The optimal glucose concentration for maximum expression of glucoamylase in chromosome-integrated recombinant yeast was lower than that in plasmid-harboring recombinant yeast.     

Mathematical modeling and genetic algorithm optimization of clove oil extraction with supercritical carbon dioxide

In the present study, a mathematical modeling for extraction of oil from clove buds using supercritical carbon dioxide was performed. Mass transfer is based on local equilibrium between solvent and solid. The model was solved numerically, and model estimation was validated using experimental data. For optimization, the clove oil equilibrium constant between solid and supercritical phase was determined by a theoretical method using fugacity concept, consequently the genetic algorithm for obtaining optimal operational conditions was used. The optimal conditions which obtained the highest amount of clove oil were pressure of 10 MPa and temperature of 304.2 K.     

Enhancement of secreted production of glucoamylase through fed-batch bioreactor culture of recombinant yeast harboring glucose-controllable <Emphasis Type="Italic">SUC2</Emphasis> promoter

Glucoamylase that hydrolyses starch to glucose is one of the important industrial enzymes for ethanol production industry. Therefore, genetic production of recombinant glucoamylase has been widely studied. Previously, we reported secreted production of Saccharomyces diastaticus-originated glucoamylase in Saccharomyces cerevisiase expression system using its own signal sequence and the SUC2 promoter that is regulated by glucose level in culture medium. In the present work, we performed a comparative study between batch and fed-batch bioreactor cultures for secreted production of recombinant glucoamylase. Through maintaining low glucose levels in the culture broth, we obtained about 7-fold higher secreted production levels of glucoamlyase in fed-batch culture. Fed-batch culture strategy also enhanced (∼3.1-fold) secretion efficiency of recombinant glucoamylase in S. cerevisiae.     

Cyclic adsorption separation processes: analysis strategy and optimization procedure

An innovative analysis strategy and an optimization procedure have been developed with the purpose of design, evaluation and optimization of small- and large-scale units of cyclic adsorption processes using the classical Skarstrom's cycle: pressure swing adsorption (PSA) and vacuum swing adsorption (VSA).The system of partial differential equations of the dynamic simulator model was solved using a recent numerical technique developed within our group, based on an adaptive multiresolution approach, thus ensuring stability and accuracy. The simulator provides models for the multiple phenomena involved in fixed-bed adsorption: pressure drop, mass transfer resistance and energy balance.An extended parametric analysis is presented for the particular case of oxygen production from air by PSA and VSA: influence of the normalized purge flow rate, the high and low pressure values, dimensionless pressurization time, dimensionless production time, pressure drop and temperature in the bed.     

Chamomile extraction with supercritical carbon dioxide: Mathematical modeling and optimization

Supercritical fluid extraction of chamomile using carbon dioxide was investigated in the current study. A model that accounts for both particle and fluid phase was presented for the supercritical extraction. The distribution coefficient of chamomile extract, between solid and solvent has been determined using genetic algorithm method. The model was solved numerically and was successfully validated with experimental data. The model was found to give superior results when compared to experimental data. The effect of particle diameter on extraction yield was investigated using the proposed model. Using genetic algorithm optimization technique 313.15 K and 20 MPa were found as the optimum temperature and pressure, respectively.     

Conceptual design and optimization of chemical processes under uncertainty by two-stage programming

This contribution presents a method and a tool for modelling and optimizing process superstructures in the early phase of process design where the models of the processing units and other data are inaccurate. To adequately deal with this uncertainty, we employ a two-stage formulation where the operational parameters can be adapted to the realization of the uncertainty while the design parameters are the first-stage decisions. The uncertainty is represented by a set of discrete scenarios and the optimization problem is solved by stage decomposition. The approach is implemented in the computer tool FSOpt (Flow sheet Superstructure Optimization) FSOpt provides a flexible environment for the modelling of the unit operations and the generation of superstructures and algorithms for the translation of the superstructure into non-linear programming models.The approach is applied to two case studies, the hydroformylation of dodec-1-ene and the separation of an azeotropic mixture of water and formic acid.     

Mathematical modeling of reverse osmosis systems

The present investigation pertains to modeling of seawater desalination system. A simulation model was developed and verified for a small-scale reverse osmosis system. The proposed model combines material balances on the feed tank, membrane module andproduct tank with membrane mass transfer models. Finally a comprehensive simulation model has been developed incorporating the effect of mass transfer inhibition The model is non-linear differential equation representing the feed concentration as a function of operating time and space. The solution of the simultaneous differential equations was obtained using the fourth order Runge-Kutta method, due to self starting and stability. The model was verified using the experimental data from the literature [17,24]. Parameter sensitivity was carried out to select the proper step size. The simulation was run for over 1000 11 enabling a prediction of operational performance at high overall system recoveries.     

Freeze drying process: real time model and optimization

Freeze drying is a separation process based on the sublimation phenomenon. This process has the following advantages compared to the conventional drying process: the material structure is maintained, moisture is removed at low temperature (reduced transport rates), product stability during the storage is increased, the fast transition of the moisturized product to be dehydrated minimizes several degradation reactions. Freeze drying process has not been studied well enough. In order to put it to practice, a mathematical model based on fundamental mass and energy balance equations has been developed, based on a deterministic mathematical model proposed by Liapis and Sadikoglu [Drying Technol. 15 (3–4) (1997) 791], and used to calculate the amount of removed water and amount of residual water. The proposed model contains the freeze drying equations, which are solved by the orthogonal collocation and polynomial approximation—Jacobi method. The results show that the dynamic mathematical model represents well the process and is especially well suited for real time optimization. As a case study to illustrate the model utilization in a real time optimization procedure, the freeze drying process was optimized by the method of Successive Quadratic Programming (SQP) used for solution of non-linear equations, for skimmed milk and soluble coffee. The optimization procedure showed to be an important tool to improve the process performance since lower energy consumption and hence lower cost has been achieved to obtain the product with the same quality.     

Ultrafiltration modeling of multiple solutes system for continuous cross-flow process

A mathematical model suitable for the multiple solutes system in continuous cross-flow ultrafiltration is developed. This model is based on mass balance analysis coupled with the filtration theory (osmotic pressure model, Kozeny-Carman equation), resistance-in-series model and gel polarization model. This model is characterized by the parameters R_m, P_m, K_b,K_bi and k_i. These parameters are estimated by using the Levenberg-Marquardt method coupled with the Gauss-Newton algorithm based on the experimental data obtained from the treatment of pretreated palm oil mill effluent (POME) as a feed in the pilot plant scale ultrafiltration system. The pretreated POME is composed of a ternary system with the solutes of carbohydrate constituents, crude protein and ammoniacal nitrogen. The simulation results show a good agreement with the experimental data. The proposed model is suitable for predicting the performance of multiple solutes in an ultrafiltration process. The concentration of each solute present is correlated with the COD value of the permeate stream.     

Novel bound contraction procedure for global optimization of bilinear MINLP problems with applications to water management problems

We propose a new method to obtain the global optimum of MINLP problems containing bilinearities. Our special method that contracts the bounds of one variable at a time allows reducing the gap between a linear lower bound and an upper bound obtained solving the original problem. Unlike some methods based on variable partitioning, our bound contraction procedure does not introduce new integers or intervals. We illustrate the method by applying it to water management problems.     

Robust processes through latent variable modeling and optimization

A data‐based approach for developing robust processes is presented and illustrated with an application to an industrial membrane manufacturing process. Using historical process data, principal component analysis and partial least squares are used to extract models of the process and of the sensitivities of the process to various disturbances, including raw material variations, environmental conditions, and process equipment differences. Robustness measures are presented to quantify the robustness of the process to each of these disturbances. The process is then made robust (insensitive) to the disturbances over which one has some control (e.g., by modifying the equipment units to which the process is sensitive and imposing specification regions on sensitive raw materials). It is also made robust to disturbances over which one has little control (e.g., environmental variations) by optimizing the process operating conditions with respect to performance and robustness measures. The optimization is easily performed in the low‐dimensional space of the latent variables even though the number of process variables involved is very large. After applying the methodology to historical data from the membrane manufacturing process, results from several months of subsequent operation are used to demonstrate the large improvement achieved in the robustness of the process. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Mathematical modeling of heat and mass transfer in hot gas spray systems

A mathematical model is developed to study simultaneous heat and mass transfer in hot gas spray systems. The model is obtained by writing mass, energy, and momentum balances for both continuous and discontinuous phases. Governing equations along with suitable correlations for heat and mass transfer coefficients have been solved numerically. In order to develop a realistic model for such complicated systems, a droplet size distribution was implemented in the model instead of using an average size. A steady state spray-cooling problem is analyzed to illustrate the applicability of the model. To validate the mathematical model for this case, necessary data was collected and measured in commercial cement plants. A good agreement between plant data and the model was noticed in general, and results obtained from the model indicate that size distribution of water droplets and physical dimensions of the spray-cooling system are important parameters. This model is very useful in determining the so-called "critical operation condition" at which sludge formation at the bottom of spray-cooling systems will happen. The predicted parameters in spray-cooling systems both for droplet phase and gas phase aptly illustrate the ability of the model to treat the complex phenomena associated with two-phase flows.     

露天矿剥采进度计划优化研究现状及发展趋势

对露天矿剥采进度优化研究的现状做了概括，对国内外有代表性的研究方法及数学模型（整数规划、目标规划、动态规划、系统模型法等）进行介绍与评价，并对该领域研究发展趋势（如人工智能法、综合方法）做了分析。     

Modelling the mechanical properties of yeast cells

An analytical model has been developed to describe the compression of a single yeast cell between parallel flat surfaces. Such cells were considered to be thin walled, liquid filled, spheres. Because yeast cells can be compressed at high deformation rates, time dependent effects such as water loss during compression and visco-elasticity of the cell wall could be and were neglected in the model. As in previously published work, a linear elastic constitutive equation was assumed for the material of the cell walls. However, yeast compression to failure requires large deformations, with high wall strains and associated rotations. New model equations appropriate to such high strains with rotations were therefore developed, based on work-conjugate Kirchhoff stresses and Hencky strains. This is an improvement on the earlier use of infinitesimal strains, and on the alternative of Green strains and 2nd Piola-Kirchhoff stresses. It is shown that the choice of stress and strain definition has a significant influence on model predictions for given wall material properties, and will affect estimates of the wall elastic modulus or other wall material property parameters obtained by fitting experimental data.     

Mathematical modeling of an in-line low-NOx calciner

The reduction of the NO_x content in in-line-calciner-type kiln systems can be made by optimization of the primary firing in the rotary kiln and of the secondary firing in the calciner. Because the optimization of calciner offers greater opportunities the mathematical modeling of this reactor is very important. A heterogeneous, dynamic mathematical model for an in-line low-NO_x calciner based on non-isothermal diffusion-reaction models for char combustion and limestone calcination has been developed. The importance of the rate at which preheated combustion air was mixed into the main flow was particularly studied. The results of the simulations indicate that the external heat and mass transfer to the char particles is not limiting. Internal diffusion of O₂, CO, NO and CO₂ is important especially in the reducing zone and the first part of the oxidizing zone of the calciner and the internal heat transport limitation is significant for the endothermic limestone calcination. The rate at which preheated combustion air is mixed into the main flow directly influences the coal combustion rate, and thereby through the rate of heat release from combustion, it also influences the calcination rate and the temperature profile. The mixing rate has some influence on the CO concentration profile and an important influence on the overall degree of fuel-N to NO conversion.     

Response surface methodology for optimizing the induction conditions of recombinant interferon beta during high cell density culture

A human interferon beta expressed from a synthetic gene was produced in high cell density culture by recombinant Escherichia coli using an optimized linear feeding strategy. The optimal induction conditions to be determined consisted of inducer concentration and dry cell weight at the time of induction. For this purpose, the response surface methodology was applied. Under optimal conditions, the maximum interferon beta concentration and overall productivity of 2.2 g/l and 0.151 g/l h were obtained, respectively, as the highest amounts ever reported for this protein. Two optimal ranges of dry cell weight and IPTG concentration consisting of 50 g/l and 2.54 mM, and 70 g/l and 1.29 mM were predicted, respectively, at which maximum productivity was achieved. By using a novel feeding strategy with linear variation of specific growth rate during high cell density fermentation, the maximum biomass productivity of 5.037 g/l h was obtained in a defined medium during 16 h. Then, by applying the optimum induction conditions, we accomplished an increase in overall productivity by more than three-fold over the central point. This is the first report showing the high production of human interferon beta by a synthetic gene in a simple fed-batch high cell density culture of recombinant E. coli in a defined medium.     

Mathematical Modeling and Simulation of Ozonation Processes in a Downstream Static Mixer with Sieve Plates

New standards for drinking water disinfection require better optimization of the ozonation stage on the basis of the concentration×contact time (CT) concept, and production of ozone from pure oxygen at higher concentrations presumes application of the new type of contactors operating efficiently at lower gas/liquid volumetric ratios. One possible construction to meet these requirements is a downstream static mixer with sieve plates. At higher flow rates of liquid in this mixer, the interfacial area may reach 10,000m²/m³ at energy dissipation 1–5kW/m³. Due to the very intensive hydrodynamic regime the ozone utilization degree in the gas phase reaches 98–100% in natural lake water ozonation. Mathematical simulation of lake water ozonation in this mixer indicated that the process proceeds mostly in the diffusion or kinetic regime depending on the operating parameters. The dominating parameters besides the sieve geometry are the liquid flow rate in the holes of the sieves and the volumetric liquid/gas ratio.     

Chromatographic separation of wood model constituents—Mathematical modeling and parameter estimation

A mathematical model of the hydrophobic adsorption chromatographic separation of wood model constituents has been developed. Veratryl alcohol was selected to illustrate a lignin molecule and salicin was selected to illustrate a lignin–carbohydrate complex. A variety of available experimental methods in combination with parameter fitting was used to estimate the parameters of packed bed porosity, axial dispersion, film mass transfer, diffusivities and adsorption equilibria with a phenylic silica stationary phase. The model was verified to simulate the separation to within an accuracy of 95%. The model was, however, unable to predict the phenomenon of elution curve fronting, caused by the channeling of the packed bed.     

Mathematical modeling of fed-batch butanol fermentation with simultaneous pervaporation

A mathematical model was developed to describe a fed-batch acetone-butanol-ethanol (ABE) fermentation with simultaneous pervaporation. The model predicted satisfactorily batch or fed-batch fermentation with or without pervaporalion by introducing a parameter reflecting cell activity loss during fed-batch fermentation with pervaporation. The model also predicted the effect of membrane area, membrane thickness, and sweep air flow rate on glucose consumption rate and residual butanol concentration in the fermentation broth. Glucose consumption rate increased by 30% by either doubling the membrane area or decreasing membrane thickness by half.     

Response surface modeling and optimization of biodiesel production from Cynara cardunculus oil

Cardoon (Cynara cardunculus L.) is a perennial spontaneous thistle grown in Mediterranean countries and well adapted to marginal lands, recently considered as a non‐food energy crop. Their seeds contain 24% of oil (dry basis). In this study, modeling and optimization of the production of fatty acid methyl esters (FAME) from cardoon oil for biodiesel uses was performed at laboratory scale, via response surface methodology, following a central composite rotatable design. FAME were obtained by transesterification of crude cardoon oil with methanol in the presence of a catalyst (sodium methoxide) for 120 min. The temperature ranged from 26 to 94 °C, the amount of sodium methoxide varied between 0.12 and 2.5 wt‐% and the molar ratio methanol/oil from 0.95 : 1 to 11 : 1. The estimated yield of FAME (97%) was obtained after 30 min, at 52 °C, for a molar ratio of 6.4 : 1 and 1.4 wt‐% of catalyst. In laboratory‐scale model validation experiments, 94% of FAME yield was obtained after 30 min of reaction. Transesterification was performed in a 30‐L reactor, under previously optimized conditions: A yield of 88% FAME was obtained after 90 min of reaction time, due to mass transfer limitations. After purification, the biodiesel showed high quality according to DIN EN 14214 standard specifications.